Factory ammo isn't always replicated either. But they don't mention that.
The big sticking point in the case was the prosecution not being able to replicate the ballistic performance and powder residues to back up Mr. Bias' story. From my understanding, mas did what he could for Mr. Bias, but he ended up doing some jail time. The reason Mas is so adamant about using factory or LEO ammunition is for both civil and criminal reasons. The civil part being the defense that the ammunition you used was recommended by a police officer, or was the regular duty issue ammunition issued by the local police. The criminal part is simple in that if you use a factory load that is easily traceable by investigators, ballistic performance and powder residues can be easily verified, along with your story of how things went down......
Keep samples of your loading batch and records. There is no reason why this should be an issue. The factory will have samples from each lot. So can you.
If you did not use factory loaded ammo for which exemplar testing ammo is available from the manufacturer, then you could be unable to introduce a potentially vital piece of evidence in your own defense (i.e., the GPR pattern that shows the badguy was six feet away with the knife, as opposed to thirty feet away like the prosecutor claims).